In recent years, with the advancement of science and technology, digital televisions begin to be incorporated into daily life. Thin Film Transistor Liquid Crystal Displays (TFT-LCDs) become currently dominant products for their features of small sizes, low power consumption, being free of radiation and high resolution.
At present, a wide-viewing high-transmittance flat-panel display technology comprises: Advanced Super Dimension Switch (ADSDS, simply referred to as ADS) and In-plane Switching (IPS). ADS technology, by utilizing a multi-dimensional electric field, constituted by an electric field generated from edges of slit-electrodes in a same plane and an electric field generated between a slit-electrode layer and a plate-like electrode layer, enables liquid crystal molecules in all orientations between the slit-electrodes and over the electrodes within a liquid crystal cell to rotate, thereby improving work efficiency of the liquid crystal and increasing light transmission efficiency. ADS technology can improve image quality of a TFT-LCD product, makes it have advantages of high resolution, high transmittance, low power consumption, wide viewing angle, high aperture ratio, low chromatic aberration, and being free of push Mura, etc.
As an improved ADS technology, HADS (High transmittance—Advanced Super Dimension Switch) technology has a higher light transmittance, contrast, and a wider viewing angle; therefore, HADS technology has a very broad prospect. As illustrated in FIG. 1(a) and FIG. 1(b), a structure of an existing HADS-type TFT-LCD array substrate mainly comprises: a substrate 1, a gate scan line 13, a thin film transistor (TFT), a data line 14, a pixel electrode 7 (equivalent to the plate-like electrode), a board wiring PAD region 10, a via hole 11 and a common electrode 9 (equivalent to the slit-electrode). The TFT-LCD array substrate is accomplished through several times of patterning process, in which each patterning process respectively comprises masking, exposing, developing, etching and removing, etc.; a specific manufacturing method of the TFT-LCD array substrate comprises the following steps. Patterns of a gate electrode 2 and a gate scan line 13 are formed on a substrate 1; a gate insulating layer 3 is formed on the gate electrode 2 and the gate scan line 13, and then a pattern of an active layer 4 is formed on the gate insulating layer 3; then, a pixel electrode 7, a source electrode 5, a drain electrode 6 and a data line 14 are sequentially formed, and the drain electrode 6 are in direct contact with the pixel electrode 7; a passivation layer 8 is deposited on the above-described patterns, and a pattern of via hole 11 on a board wiring PAD region 10 is formed through a patterning process; thereafter, a common-electrode metal is deposited, and a pattern of a common electrode 9 with a comb-like slim structure is formed through a patterning process.
In the procedure of forming the pattern of the common electrode 9 with a comb-like slim structure (i.e., a slit-structure) through a patterning process, wet etch is usually adopted. Thus, due to the influence of some factors, for example, the deposited ITO-electrode metal being too thick, or the base substrate having defects, the part of the ITO-electrode metal that is not covered with photoresist may not be completely etched off by the etching liquid, which eventually leads to residues of electrodes. Thus, a uniform pattern of comb-like electrode cannot be formed, so that an uneven screen image is displayed, which seriously affects the yield and costs of array substrates.